Lubricating oil composition

ABSTRACT

A lubricating oil composition includes: a lubricating base oil; and an imide compound, an amide compound and an aliphatic amine compound mixed with the lubricating base oil. A content of the imide compound is 300 to 1000 ppm by mass of the total amount of the composition in terms of nitrogen. A content of the amide compound is 380 to 1300 ppm by mass of the total amount of the composition in terms of nitrogen. A content of the aliphatic amine compound is 35 to 360 ppm by mass of the total amount of the composition in terms of nitrogen.

TECHNICAL FIELD

The present invention relates to a lubricant oil composition used for anautomatic transmission such as a multistage transmission and acontinuously variable transmission.

BACKGROUND ART

A lubricating oil composition used for an automatic transmission such asa multistage transmission and a continuously variable transmission isrequired to have a high power (torque) transmission volume. Accordingly,various lubricating oil compositions for an automatic transmission thatcan favorably transmit power with a large power transmission volume havebeen known (see, for instance, Patent Documents 1 and 2).

A lubricating oil composition disclosed in Patent Document 1 is amixture of a sulfur extreme pressure agent, a phosphorous extremepressure agent and an alkali earth metal detergent with a lubricatingbase oil so that the lubricating oil composition exhibits an excellentwear resistance and extreme-pressure property, maintains a high frictioncoefficient for a long period and transmits a large volume of torque.

A lubricating oil composition disclosed in Patent Document 2 is amixture of an effective amount of bisimide succinate having apredetermined structure with a lubricating base oil for enhancing apower transmission volume and improving anti-shudder property.

Patent Document 1: JP-A-9-100487

Patent Document 2: JP-A-9-202890

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

In addition to a high coefficient of static friction (μs) as an index oftransmission torque at engagement of the clutch, it is also required asa clutch friction property for an automatic transmission that a “ratio(μo/μd) of a friction coefficient to a coefficient of kinetic frictionjust before stopping,” which is an index allowing for smoothtransmission by preventing transmission shock (shudder), is sufficientlysmall, e.g., 1.05 or less. On the other hand, new automobiles in themarket, which have a variety of types by domestic and foreignmanufacturers, have a variety of materials and mechanisms for a clutchused therein. The clutch further exhibits a variety of degree of agingdeterioration.

However, the lubricating oil compositions disclosed in Patent Documents1 and 2 have not provided a sufficient clutch friction property yet.

An object of the present invention is to provide a lubricating oilcomposition balancing both of a high transmission torque at engagementof the clutch and a high transmission-shock prevention in an automatictransmission such as a multistage transmission and a continuouslyvariable transmission.

Means for Solving the Problems

In order to solve the above-mentioned problems, according to an aspectof the invention, there is provided a lubricating oil compositiondescribed below.

[1] A lubricating oil composition including: a lubricating base oil; andan imide compound, an amide compound and an aliphatic amine compoundmixed with the lubricating base oil, in which a content of the imidecompound is 300 to 1000 ppm by mass of a total amount of the compositionin terms of nitrogen; a content of the amide compound is 380 to 1300 ppmby mass of the total amount of the composition in terms of nitrogen; anda content of the aliphatic amine compound is 35 to 360 ppm by mass ofthe total amount of the composition in terms of nitrogen.[2] The lubricating oil composition according to the above aspect of theinvention, in which the contents of the imide compound, the amidecompound and the aliphatic amine compound amount to 1000 to 2000 ppm bymass of the total amount of the composition in terms of nitrogen.[3] The lubricating oil composition according to the above aspect of theinvention, in which the imide compound is a succinimide compound.[4] The lubricating oil composition according to the above aspect of theinvention, in which the lubricating oil composition is used for amultistage transmission or a continuously variable transmission.[5] The lubricating oil composition according to the above aspect of theinvention, in which the continuously variable transmission is abelt-type continuously variable transmission equipped with a metallicbelt.

According to the lubricating oil composition of the aspect of theinvention, since the predetermined amounts of three specified organicnitrogen compounds (the imide compound, the amide compound and thealiphatic amine compound) are mixed with the base oil, the coefficientof static friction (μs) is high, resulting in a high transmissiontorque. Further, when used for an automatic transmission such as amultistage transmission and a continuously variable transmission, thelubricating oil composition of the aspect of the invention exhibits anexcellent anti-shock transmission property (anti-shudder property)without decreasing transmission torque. Particularly, the lubricatingoil composition of the aspect of the invention is preferably used for abelt-type continuously variable transmission equipped with a metallicbelt.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred exemplary embodiment for implementing the invention will bedescribed below.

[Arrangement of Lubricating Oil Composition]

A lubricating oil composition of an aspect of the invention is providedby mixing at least an imide compound, amide compound and aliphatic aminecompound with a lubricating base oil. The invention will be describedbelow in detail.

(Lubricating Base Oil)

As the lubricating base oil, at least one of a mineral oil and asynthetic oil may be used alone or in a combination of two types ormore, or a combination of the mineral oil and the synthetic oil may beused.

Such mineral oil and synthetic oil are not particularly limited, but anymineral oil and synthetic oil are applicable as long as they aregenerally usable as a base oil for a transmission. Particularly, thelubricating base oil preferably has a kinematic viscosity of 1 mm²/s to50 mm²/s, more preferably 2 mm²/s to 15 mm²/s at 100 degrees C. When thekinematic viscosity is too high, a low temperature viscosity may bedeteriorated. When the kinematic viscosity is too low, wear at a slidingportion such as a gear bearing and a clutch in the continuously variabletransmission may be increased. Accordingly, the lubricating base oilpreferably has the kinematic viscosity of 1 mm²/s to 50 mm²/s, morepreferably 2 mm²/s to 15 mm²/s at 100 degrees C.

A pour point, which is an index of a low temperature fluidity of thelubricating base oil, is not limited, but is preferably minus 10 degreesC. or lower, particularly minus 15 degrees C. or lower.

The lubricating base oil is not particularly limited, but preferably hasa saturated hydrocarbon component of 90 mass % or more, a sulfurcomponent of 0.03 mass % or less and a viscosity index of 100 or more.When the saturated hydrocarbon component is less than 90 mass %,degraded products may be increased. Moreover, when the sulfur componentis more than 0.03 mass %, degraded products may be increased. Further,when the viscosity index is less than 100, wear at a high temperaturemay be increased. Consequently, the mineral oil and synthetic oil havingthe saturated hydrocarbon component of 90 mass % or more, the sulfurcomponent of 0.03 mass % or less and the viscosity index of 100 or moremay be preferably used.

Examples of the mineral oil include a paraffinic mineral oil, anintermediate base mineral oil and a naphthenic mineral oil.Specifically, the mineral oil is exemplified by a light neutral oil, amedium neutral oil, a heavy neutral oil, bright stock and the like thatare produced by solvent purification or hydrogenation purification.

Examples of the synthetic oil include poly-α-olefins, α-olefincopolymers, polybutene, alkyl benzene, polyol esters, diacid esters,polyoxyalkylene glycol, polyoxyalkylene glycol esters, polyoxyalkyleneglycol ethers, hindered esters, silicone oil and the like. Polyolefinsand polyol esters are particularly preferable.

(Imide Compound)

As the imide compound mixed in the lubricating oil composition of theaspect of the invention, a succinimide is preferable in terms of anincrease in μ ratio and consequent excellent anti-shudder property.Particularly, the succinimide preferably has an alkyl group or analkenyl group of a number average molecular weight of 500 to 3000 in aside chain. Various succinimides can be listed as the above succimide,examples of which include a succinimide having a polybutenyl group and asuccinimide having a polyisobutenyl group. The polybutenyl group meanspolymerized mixture of 1-butene and isobutene, polymerized highly-pureisobutene or a hydrogenerated polyisobutenyl group. The succinimide maybe so-called mono-type alkenylsuccinimide or alkylsuccinimide, orso-called bis-type alkenylsuccinimide or alkylsuccinimide.

Succinimides having a side chain may be manufactured by any conventionalmethods. In order to manufacture polybutenyl succinimide, for instance,polybutene or chlorinated polybutene having a number average molecularweight of approximately 500 to 3,000 is reacted with maleic anhydride atapproximately 100 to 200 degrees C. to form polybutenyl succinic acid,and the obtained polybutenyl succinic acid is reacted with polyamine.

Examples of polyamine are diethylene triamine, triethylene tetramine,tetraethylene pentamine, pentaethylene hexamine and the like.

The alkyl or alkenyl-succinimide may be an alkylphenol derivative or asulfurized alkylphenol derivative in which the alkyl oralkenyl-succinimide is fused with an aromatic compound such asalkylphenol or sulfurized alkylphenol by Mannich condensation. The alkylgroup of the alkylphenol typically has 3 to 30 carbon atoms.

The succinimide, which has in the side chain an alkyl or alkenyl grouphaving a number average molecular weight of 500 to 3,000, unfavorablyexhibits deteriorated dispersibility into the base oil when the numberaverage molecular weight of the side chain is less than 500. On theother hand, when the number average molecular weight of the side chainis more than 3000, the handleability in preparing the lubricating oilcomposition is deteriorated. Moreover, when the composition having anexcessively increased viscosity is applied to, for instance, a wetclutch, a friction property of the composition may be deteriorated.

The above succinimide is also preferably boron-modified in use. Forinstance, in order to manufacture boronated polybutenyl succinimide, anorganic solvent such as alcohols, hexane or xylene is added withpolyamine, polybutenyl succinic acid (anhydride) and a boron compoundsuch as boracic acid, and is subsequently heated under suitableconditions. Besides boracic acid, examples of the boron compound includeboric anhydride, boron halogenide, borate ester, amide borate, boricoxide and the like. Among the above, boracic acid is particularlypreferable.

The boron-modified succinimide can increase a coefficient of kineticfriction because of its bulky structure when mixed in the composition,thereby preferably providing increased transmission torque.

When the boron-modified succinimide is mixed in the composition, a boroncontent is preferably 50 to 3,000 ppm by mass of a total amount of thecomposition, more preferably 50 to 2,500 ppm by mass. When the boroncontent is 50 ppm by mass or more, heat resistance of the preparedlubricating oil composition is enhanced. When the boron content is 3,000ppm by mass or less, it is preferable that hydrolysis of boron portionscan be restrained and manufacturing cost can also be reduced.

A nitrogen content derived from the imide compound mixed in thelubricating oil composition of the aspect of the invention isnecessarily 300 to 1000 ppm by mass of the total amount of thecomposition, preferably 400 to 800 ppm by mass._(n) When the nitrogencontent derived from the imide compound is less than 300 ppm by mass,the prepared lubricating oil composition provides insufficienttransmission torque. When the nitrogen content derived from the imidecompound is more than 1000 ppm by mass, the prepared lubricating oilcomposition exhibits large transmission shock. Moreover, when themineral oil is used as the base oil, solubility of the composition isdeteriorated.

(Amide Compound)

An amide compound mixed in the lubricating oil composition of the aspectof the invention is exemplified by fatty acid amide obtained by fusing afatty acid to an amine (including ammonia).

The fatty acid is preferably a saturated/unsaturated or linear/branchedfatty acid having 8 to 30 carbon atoms. In addition, the fatty acid maybe a monobasic acid or polybasic acid. Specifically, examples of thefatty acid include caprylic acid, pelargonic acid, capric acid, lauricacid (lauryl acid), isolauric acid, myristic acid, isomyristic acid,pentadecyl acid, palmitic acid, palmitoyl acid, margaric acid, stearicacid, isostearic acid, oleic acid, vaccenic acid, linoleic acid, malonicacid, succinic acid, sebacic acid and the like.

Examples of the amine include: ammonia; alkyl amines (an alkyl group maybe linear or branched) such as monomethylamine, monoethylamine,monopropylamine, monobutylamine, monopentylamine, monohexylamine,monoheptylamine, monooctylamine, dimethylamine, methylethylamine,diethylamine, methylpropylamine, ethylpropylamine, dipropylamine,methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine,dipentylamine, dihexylamine, diheptylamine and dioctylamine; alkanolamines (an alkanol group may be linear or branched) such asmonomethanolamine, monoethanolamine, monopropanolamine,monobutanolamine, monopentanolamine, monohexanolamine,monoheptanolamine, monooctanolamine, monononanolamine, dimethanolamine,methanolethanolamine, diethanolamine, methanolpropanolamine,ethanolpropanolamine, dipropanolamine, methanolbutanolamine,ethanolbutanolamine, propanolbutanolamine, dibutanolamine,dipentanolamine, dihexanolamine, diheptanolamine and diooctanolamine;and a mixture thereof.

Further, besides the above monoamines, a so-called polyamine having aplurality of amino groups in a molecule is suitable as the amine.Examples of the polyamine include diethylene triamine, triethylenetetramine, tetraethylene pentamine, pentaethylene hexamine and the like.

Suitable examples of the amide compound obtained by fusing the fattyacid to the amine as described above include: a polyamide obtained byfusing isostearic acid to polyamines such as triamine, tetraamine andpentamine; a polyamide obtained by fusing oleic acid to a polyamine; anda polyamide obtained by fusing lauric acid to a polyamine.

A nitrogen content derived from the amide compound mixed in thelubricating oil composition of the aspect of the invention isnecessarily 380 to 1300 ppm by mass of the total amount of thecomposition, preferably 500 to 1000 ppm by mass. When the nitrogencontent derived from the amide compound is less than 380 ppm by mass,the prepared lubricating oil composition exhibits insufficientanti-shock transmission property. When the nitrogen content derived fromthe amide compound is more than 1300 ppm by mass, the preparedlubricating oil composition is deficient in transmission torque.

(Aliphatic Amine Compound)

Among aliphatic amine compounds used for producing the above amidecompounds, an aliphatic amine compound mixed in the lubricating oilcomposition of the aspect of the invention preferably has a relativelyhigh molecular weight. Specifically, examples of the aliphatic aminecompound include oleylamine, stearylamine and isostearylamine.

Moreover, the aliphatic amine compound may not be used singularly, butpreferably used in a form such as a mixed fatty acid amine and beeftallow propylenediamine.

A nitrogen content derived from the aliphatic amine compound mixed inthe lubricating oil composition of the aspect of the invention isnecessarily 35 to 360 ppm by mass of the total amount of thecomposition, preferably 100 to 300 ppm by mass. When the nitrogencontent derived from the aliphatic amine compound is less than 35 ppm bymass, the prepared lubricating oil composition exhibits insufficientinitial anti-shock transmission property. When the nitrogen contentderived from the aliphatic amine compound is more than 360 ppm by mass,the prepared lubricating oil composition is deficient in transmissiontorque and exhibits unfavorable durability due to sludge generation.

In the lubricating oil composition of the aspect of the invention, thecontents of the imide compound, amide compound and aliphatic aminecompound described above preferably amount to 1000 to 2000 ppm by massof the total amount of the composition in terms of nitrogen, morepreferably 1100 to 1900 ppm by mass.

In other words, when the contents of the three components are within theabove-described range, transmission torque and anti-shock transmissionproperty, which are wet clutch performance generally in a trade-offrelation, can be more fully satisfied

(Other Additives)

The lubricating oil composition of the aspect of the invention may beadded with an additive as long as an object of the invention to reliablyprovide less transmission shock and high transmission torque isachieved.

Examples of the additive include an antioxidant, a metal deactivator, anantifoaming agent, a viscosity index improver, a pour point depressant,a surfactant, a coloring agent and the like.

Examples of the antioxidant include an amine antioxidant, a phenolicantioxidant, a sulfuric antioxidant and the like.

Examples of the amine antioxidant include: monoalkyldiphenylamines suchas monooctyldiphenylamine and monononyldiphenylamine;dialkyldiphenylamines such as 4,4′-dibutyldiphenylamine,4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine,4,4′-diheptyldiphenylamine, 4,4′-dioctyldiphenylamine and4,4′-dinonyldiphenylamine; polyalkyldiphenylamines such astetrabutyldiphenylamine, tetrahexyldiphenylamine,tetraoctyldiphenylamine and tetranonyldiphenylamine; and naphthylaminessuch as α-naphthylamine, phenyl-α-naphthylamine,butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine,hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine,octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine.Particularly, the amine antioxidant preferably has an alkyl group of 4to 24 carbon atoms, more preferably 6 to 18 carbon atoms. One of theabove amine antioxidants may be used alone or a combination of two ormore thereof may be used.

Examples of the phenolic antioxidant include 2,6-di-t-butylphenol,2,6-di-t-butyl-4-methylphenol, 4,4′-methylene-bis(2,6-di-t-butylphenol),4,4′-butylidene-bis(3-methyl-6-t-butylphenol),2,2′-methylene-bis(4-ethyl-6-t-butylphenol),2,2′-methylene-bis(4-methyl-6-t-butylphenol),4,4′-isopropylidene-bisphenol, 2,4-dimethyl-6-t-butylphenol,tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane,1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzil)benzene,2,6-di-t-butyl-4-ethylphenol and the like.

Examples of the sulfuric antioxidant include, dialkylthiodipropionate, aderivative of dialkyldithio-carbamic acid (except a metal salt),bis(3,5-di-t-butyl-4-hydroxybenzil)sulfide, mercaptobenzothiazole, areactant of phosphorus pentasulfide and olefin, dicetyl sulfide and thelike.

One of the above various antioxidants may be used alone or a combinationof two or more thereof may be used. Particularly, the amine antioxidant,phenolic antioxidant or zinc alkyldithiophosphate are preferably used. Acontent of such an antioxidant is preferably in a range from 0.05 to 3mass % of the total amount of the composition.

The metal deactivator is exemplified by benzotriazole and thiadiazole,which may be used alone or in a combination of two or more. A content ofsuch a metal deactivator is preferably in a range from 0.01 to 5 mass %of the total amount of the composition.

Examples of the antifoaming agent include a silicone compound and anester compound, which may be used alone or in a combination of two ormore. A content of such an antifoaming agent is preferably in a rangefrom 0.05 to 5 mass % of the total amount of the composition.

Examples of the viscosity index improver include polymethacrylate, anolefin copolymer such as an ethylene-propylene copolymer, a dispersedolefin copolymer, a styrene copolymer such as a hydrogenatedstyrene-diene copolymer, which may be used alone or in a combination oftwo or more thereof. A content of such a viscosity index improver ispreferably in a range from 0.01 to 10 mass % of the total amount of thecomposition.

The pour point depressant may be exemplified by polymethacrylate. Acontent of such a pour point depressant is preferably in a range from0.01 to 10 mass % of the total amount of the composition.

The surfactant may be exemplified by polyoxyethylene alkylphenyl ether.A content of such a surfactant is preferably in a range from 0.01 to 10mass % of the total amount of the composition.

The lubricating oil composition of the above aspect of the invention canbe used for various automatic transmissions such as a multistagetransmission, a chain type continuously variable transmission equippedwith a chain, a belt-type continuously variable transmission equippedwith a metallic belt or a traction-drive type continuously variabletransmission equipped with a traction-drive.

EXAMPLES

The invention will be described in more detail below with reference toexamples and comparatives.

The invention should not be construed as limited to what is described inthe examples and the like.

Examples 1 to 9 and Comparatives 1 to 6

Lubricating oil compositions as shown in Tables 1 and 2 were prepared.The prepared lubricating oil compositions were evaluated on coefficientof kinetic friction (μd) and coefficient of static friction (μo) whenbeing dynamic and coefficient of static friction (μs) when being staticwith use of SAE No. 2 friction testing machine under the followingexperimental conditions (based on JASOM348-2002). Specifically, theevaluation was carried out with a cellulose clutch material used for apractical transmission under the conditions of surface pressure being0.2 to 0.3 N/mm², oil temperature being 100 degrees C., dynamic rotationspeed being 3000 rpm and static rotation speed being 0.7 rpm.

Under the above experimental conditions, μd and μs at 3000 cycles weremeasured and μ ratio (μo/μd) was obtained. When μs is more than 0.1,transmission torque is practically high enough. When μ ratio is 1 orless, anti-shock transmission property is excellent.

The results are shown in Table 1 and Table 2. Components used arerespectively shown below.

(1) Lubricating base oil: Paraffinic base oil having a pour point ofminus 30 degrees C., a kinematic viscosity at 100 degrees C. of 3.5mm²/s and % C_(A) being 0.1 mass % or less

(2) Additive: (2-1) Component A: Imide Compound

-   -   A1: Polybutenyl succinimide    -   (polybutenyl group: 950 molecular weight (Mw); Nitrogen content        in the compound: 1.5 mass %)    -   A2: Boron-containing polybutenyl succinimide    -   (polybutenyl group: 2200 molecular weight (Mw); Nitrogen content        in the compound: 0.5 mass %)    -   A3: Polybutenyl succinimide    -   (polybutenyl group: 280 molecular weight (Mw); Nitrogen content        in the compound: 5 mass %)

(2-2) Component B: Amide Compound

-   -   B1: Polyamide obtained by fusing isostearic acid to        tetraethylenepentamine (Nitrogen content in the compound: 5 mass        %)    -   B2: Polyamide obtained by fusing oleic acid to        diethylenepentamine (Nitrogen content in the compound: 3 mass %)    -   B3: Polyamide obtained by fusing lauric acid to        hexaethylenepentamine (Nitrogen content in the compound: 8 mass        %)

(2-3) Component C: Aliphatic Amine Compound

-   -   C1: Oleylamine (Nitrogen content in the compound: 5 mass %)    -   C2: Mixed fatty acid amine (Nitrogen content in the compound: 3        mass %)    -   C3: Beef tallow propylenediamine (Nitrogen content in the        compound: 8 mass %)

(2-4) Component D: Antioxidant

-   -   D1: Alkyldiphenylamine (Nitrogen content in the compound: 4.8        mass %)

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Lubricatingoil Lubricating base oil remainder remainder remainder remainderremainder composition Additive Component A1 540 — — 540 540 (ppm by A(Imide) A2 — 300 — — — mass) A3 — — 950 — — Component B B1 650 650 650 —— (Amide) B2 — — — 380 — B3 — — — — 1300 Component C C1 170 170 170 170— (Aliphatic C2 — — — — 35 amine) C3 — — — — — A + B + C (Total) 13601120 1770 1090 1875 Component D 140 — — — — (antioxidant) Evaluationresult SAENo2 μs 0.122 0.105 0.135 0.115 0.110 μ0/μd 0.94 0.88 0.99 0.940.96 Example 6 Example 7 Example 8 Example 9 Lubricating oil Lubricatingbase oil remainder remainder remainder remainder composition AdditiveComponent A1 540 — 540 — (ppm by A (Imide) A2 — — — — mass) A3 — 950 —950 Component B B1 650 — — 650 (Amide) B2 — 380 350 — B3 — — — —Component C C1 — — 170 170 (Aliphatic C2 35 — — — amine) C3 — 360 — —A + B + C (Total) 1225 1690 1060 1770 Component D — — — 140(antioxidant) Evaluation result SAENo2 μs 0.120 0.103 0.101 0.150 μ0/μd0.96 0.90 0.88 0.99

TABLE 2 Compar- Compar- Compar- Compar- Compar- Compar- ative 1 ative 2ative 3 ative 4 ative 5 ative 6 Lubricating oil Lubricating base oilremainder remainder remainder remainder remainder remainder compositionAdditive Component A1 — 280 540 — — — (ppm by A (Imide) A2 180 — — — 200— mass) A3 — — — 1500 — 1050 Component B1 — — 650 — — — B (Amide) B2 —280 — 380 — 380 B3 1300 — — — 1600 — Component C1 — — — 170 — — C(Aliphatic C2 — — — — 35 — amine) C3 360 360 — — — 450 A + B + C (Total)1840 920 1190 2050 1835 1880 Component D — — — — — — (antioxidant)Evaluation SAENo2 μs 0.05 0.08 0.09 0.15 0.09 0.08 result μ0/μd 0.820.85 1.03 1.30 0.92 0.88

[Evaluation Results]

As is understood from Examples 1 to 9 of Table 1, in each of thelubricating oil compositions of the aspect of the invention, μs is 0.1or more (i.e., transmission torque is large) and μ ratio (μo/μd) issmall at 1 or less (i.e., anti-shock transmission property isexcellent).

On the other hand, as is understood from Table 2, in Comparative 1, isextremely small since the content of the imide compound is low althoughthe contents of the amide compounds and the aliphatic amine compoundsare sufficient. Consequently, transmission torque becomes quitedeficient. In Comparative 2, μs is not sufficient since the imidecompound and the amide compound each are less contained although thecontent of the aliphatic amine compound is sufficient. Consequently,transmission torque becomes deficient. In Comparative 3, the aliphaticamine compound is not contained, so that μ ratio is large and anti-shocktransmission property is poor. In Comparative 4, since the imidecompound is excessively contained, μ ratio is large and anti-shocktransmission property is considerably poor although μs is large. InComparative 5, the content of the imide compound is excessively smalland the content of the amide compound is excessively large, so that μsis slightly low at 0.09 although μ ratio is 1 or less. Consequently,transmission torque becomes deficient. In Comparative 6, the contents ofthe imide compound and the amide compound are excessively large, so thatμs is slightly low at 0.08 although μ ratio is 1 or less. Consequently,transmission torque becomes deficient.

INDUSTRIAL APPLICABILITY

The invention is applicable as a lubricating oil composition for anautomatic transmission used for a multistage transmission and acontinuously variable transmission of a metallic belt type, a chaintype, a traction drive type and the like.

1. A lubricating oil composition comprising: a lubricating base oil; andan imide compound, an amide compound and an aliphatic amine compoundmixed with the lubricating base oil, wherein a nitrogen content of theimide compound is 300 to 1000 ppm by mass of a total amount of thecomposition; a nitrogen content of the amide compound is 380 to 1300 ppmby mass of the total amount of the composition; and a nitrogen contentof the aliphatic amine compound is 35 to 360 ppm by mass of the totalamount of the composition.
 2. The lubricating oil composition accordingto claim 1, wherein the contents of the imide compound, the amidecompound and the aliphatic amine compound amount to 1000 to 2000 ppm bymass of the total amount of the composition in terms of nitrogen.
 3. Thelubricating oil composition according to claim 1, wherein the imidecompound is a succinimide compound.
 4. The lubricating oil compositionaccording to claim 1, wherein a multistage transmission or acontinuously variable transmission comprises the lubricating oilcomposition.
 5. The lubricating oil composition according to claim 4,wherein the continuously variable transmission is a belt-typecontinuously variable transmission equipped with a metallic belt.